Crystal structure of bis[(η5-tert-butylcyclopentadienyl)tricarbonylmolybdenum(I)](Mo—Mo)

The Mo—Mo bond in the dinuclear molecular title compound is 3.2323 (3) Å, in good agreement with related dinuclear molybdenum(I) compounds with cyclopentadienyl (Cp) ligands.

The dinuclear molecule of the title compound, [Mo 2 (C 9 H 13 ) 2 (CO) 6 ] or [Mo( t BuCp)(CO) 3 ] 2 where t Bu and Cp are tert-butyl and cyclopentadienyl, is centrosymmetric and is characterized by an Mo-Mo bond length of 3.2323 (3) A ˚. Imposed by inversion symmetry, the t BuCp and the carbonyl ligands are in a transoid arrangement to each other.In the crystal, intermolecular C-H� � �O contacts lead to the formation of layers parallel to the bc plane.

Chemical context
Cyclopentadienyl (Cp) complexes can be employed as versatile precursors for the synthesis of new functional materials, including heterocycles, catalysts, organic conductors or pharmaceuticals (Absolonova ´et al., 2021;Kharitonov et al., 2022).Not only the exchange of the central metal atoms to which the Cp ligands are bound, but also the decoration of Cp ligands with functional groups can be used as a synthetic strategy to develop new catalysts (Loginov et al., 2019).Similarly to other coordination compounds (Mahmoudi et al., 2017a,b;Mahmudov & Pombeiro 2023), the interplay between electron-donating or -withdrawing functions of substituents with their non-covalent donor or acceptor character in cyclopentadienyl complexes can improve activity and selectivity of catalytic transformations.

Structural commentary
The dinuclear title complex crystallizes in the monoclinic space group P2 1 /c with half of the molecule present in the asymmetric unit (Fig. 1).The entire dimer is generated by an inversion center located at the middle of the Mo-Mo bond (Fig. 2).Imposed by inversion symmetry, the tert-butylcyclopentadienyl ( t BuCp) ligands are in a transoid arrangement about the Mo-Mo bond with that bond being 3.2323 (3) A ˚in length.For the tert-butyl groups on the ( t BuCp) ring, the Mo1 i -Mo1-C5-C6 torsion angle is 115.30(18) � .All bond angles involving the carbonyl ligands are close to linearity, with Mo1-C10 O1, Mo1-C11 O2 and Mo1-C12 O3 being 174.6 (2), 173.1 (2) and 178.2 (2) � , respectively.

Figure 2
The intra-and intermolecular hydrogen contacts within the crystal structure of the title compound.[Symmetry codes: Table 1 Hydrogen-bond geometry (A ˚, � ).

Figure 3
View of the non-classical hydrogen-bonding interactions down the a axis.
CYPMOC10 crystallizes in the monoclinic P2 1 /c space group with Z = 2, CYPMOC10 and GAKVUJ crystallize in the monoclinic P2 1 /n space group with Z = 2, while CYPMOC01 crystallizes in the monoclinic I2 space group with Z = 2, and TIVLAL in the triclinic P1 space group with Z = 1.
Although the Mo-Mo distances in these structures vary slightly depending on the steric effects caused by the groups attached to the Cp rings, the values may be compared within the error limits of the experiments.The Mo-Mo distances are 3.2239 (11) A ˚for CYPMOC01, 3.235 (1) A ˚for CYPMOC10, 3.281 (1) A ˚for GAKVUJ, and 3.253 (1) A ˚for TIVLAL.The average length of the Mo-Mo bond in these structures is 3.263 (8) A ˚, which is in agreement with the length of the Mo-Mo bond for the title compound [3.2323 (3) A ˚].In all these structures, the Mo-C O angles deviate only slightly from linearity due to the steric effects mentioned.

Synthesis and crystallization
The binuclear complex [Mo( t BuCp)(CO) 3 ] 2 was synthesized according to a reported protocol (Manning et al., 1990).Under an inert atmosphere, 195 mg (5 mmol) of sodium amide and 0.7 ml (5 mmol) of freshly distilled tert-butylcyclopentadiene in diglyme (100 ml) were heated for 3 h at 318-323 K.After the mixture had cooled to room temperature, 1.32 g (5 mmol) of molybdenum hexacarbonyl were added and the mixture heated at 423 K for 40 min.The yellow-colored reaction mixture was cooled to room temperature and 40 g of iron(III)    1948, 1912 and 1858 (C O).Deep-red crystals of the title complex suitable for single crystal X-ray analysis were grown in toluene at a temperature of 263 K.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms were included in calculated positions and treated as riding: C-H = 0.95-0.98A ˚with U iso (H) = 1.5U eq (C-methyl) and 1.2U eq (C) for other H atoms.

Special details
Geometry.All esds (except the esd in the dihedral angle between two l.s.planes) are estimated using the full covariance matrix.The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry.An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s.planes.

Figure 4
Figure 4View of the non-classical hydrogen-bonding interactions down the b axis.

Figure 5
Figure 5View of the non-classical hydrogen-bonding interactions down the c axis.

Table 2
Experimental details.